LITERAL TRANSLATION OF PCT INTERNATIONAL APPLICATION PCT/EP01/14056, AS FILED ON Dec. 1, 2001.
The invention relates to a method according to the preamble of the patent claim 1, as is known from the DE 198 14 657 A1.
In motor-driven motor vehicles, a parking brake is generally provided for arresting or fixing the motor vehicle in connection with the parking thereof. In this regard, the braking force for the parking brake should be selected only as great as necessary, in order to avoid an increased wear of the braking system. From the initially mentioned DE 198 14 657 A1 with a control and/or regulating apparatus for an electrical parking brake arrangement of motor vehicles, forming the general background of this art, it is known for this purpose to provide a sensor unit for measuring the slope of the inclined position of the vehicle; the braking force of the parking brake that is to be adjusted or set is prescribed in connection with the sensor signal of this slope sensor and thus corresponding to the established or fixed slope. However, with this information by itself, the braking force is often erroneously selected, because the actual required braking force can vary significantly also after the parking of the vehicle dependent on vehicle-specific conditions or external conditions, for example dependent on the varying loading of the vehicle, the condition of the braking system (for example due to wear or damages or defects of the braking system), the influences of the wind, or the change of the slope or inclination after the parking of the vehicle (for example upon parking in a duplex garage, on a vehicle transporter, or a ferry, etc.). The erroneous prescription or specification of the braking force can have critical situations that impair the safety as a result, especially a braking force that is too low can lead to the motor vehicle rolling away.
The underlying object of the invention is to propose a simple method for operating a motor-driven motor vehicle with a high reliability and safety.
This object is achieved according to the invention by the features in the characterizing portion of the patent claim 1. Advantageous embodiments of the method are the subject of the further patent claims.
The braking force for the (electrical) parking brake is adjusted or adapted to the current existing requirements even after the parking of the motor vehicle, that is to say the braking force for the parking brake is prescribed corresponding to the actual conditions also in the parked state of the motor vehicle. For this purpose, in connection with the parking of the motor vehicle, a first desired or nominal value is determined in connection with certain (vehicle-specific) characteristic parameters as the starting value of the braking force for the parking bake, especially in connection with the slope or inclination of the motor vehicle and/or the loading of the motor vehicle; in the parked state of the motor vehicle, this starting value of the braking force is monitored or checked in each measuring process of measuring processes that follow successively one after another at certain time intervals, in that respectively a current desired or nominal value for the braking force is determined on the basis of the measured values recorded for the (vehicle-specific) characteristic parameters in the measuring processes. As the (vehicle-specific) characteristic parameters, especially the speed and/or the acceleration of the motor vehicle are utilized as a measure for the motion of the motor vehicle, as well as the slope or inclination of the motor vehicle and the loading of the motor vehicle. If the current desired value for the braking force determined in connection with the measured values of the (vehicle-specific) characteristic parameters corresponds with the prescribed desired value, then the braking force for the (electrical) parking brake is prescribed without change, especially then if no motion of the motor vehicle takes place with the prescribed desired value for the braking force; if the current desired value for the braking force determined in connection with the measured values of the (vehicle specific) characteristic parameters deviates from the prescribed desired value, then the braking force for the (electrical) parking brake is prescribed in a corresponding adapted manner (increased or reduced), especially the desired value for the braking force is increased if a motion of the motor vehicle takes place with the prescribed desired value for the braking force. The time intervals at which the measuring processes for determining the measured values of the vehicle-specific characteristic parameters and therewith the desired value for the braking force follow successively one after another can be selected as desired in this context; especially the time intervals can be selected corresponding to the course or progression of the desired value, especially can be varied according to the time progression or course of the desired value for the braking force: for example in connection with a desired value for the braking force that remains constant or unchanged, also the time interval between the measuring processes can be maintained, and in connection with a required change of the desired value for the braking force, the time interval between the measuring processes can be shortened or reduced. The measured values of the vehicle-specific characteristic parameters recorded in the measuring processes are acquired by means of suitable sensors, especially the speed and/or the acceleration of the motor vehicle as a measure for the movement or motion of the motor vehicle by means of wheel rotational speed sensors and/or acceleration sensors, the slope or inclination of the motor vehicle by means of slope or inclination sensors, and the loading of the motor vehicle by means of spring travel sensors or loading sensors or load sensors. The desired values for the braking force to be prescribed in connection with the vehicle-specific characteristic parameters can be stored in a (multi-dimensional) characteristic value field or in a characteristic curve or in a table. The evaluation of the measured values of the vehicle-specific characteristic parameters and the prescribing of the desired values for the braking force is carried out by a control unit arranged in or on the motor vehicle, which, for example, can be integrated in a control device of the motor vehicle, or for example can be embodied as a control device of the motor vehicle.
A monitoring or checking on the parking of the motor vehicle is carried out by evaluation of criteria for certain or specific system values with the aid of plausibility considerations, for example by evaluation of at least one of the criteria for the following system values: the speed of the vehicle (this must be 0), the motor state of the motor vehicle (the motor of the motor vehicle must be stopped or switched off), the electronic key that is used for starting the operation of the motor vehicle (this ID transponder or authentication transponder must have transmitted a certain specified code), as well as the state of the doors of the motor vehicle, especially the driver""s door of the motor vehicle (a certain specified closing state/opening state must be present).
The basic informations underlying the method can be acquired in a simple manner, especially by means of sensors already present in the motor vehicle, so that advantageously the xe2x80x9ccorrectxe2x80x9d braking force for the parking brake can be prescribed after the parking of the motor vehicle in a simple and cost-effective or economical manner, without the operator of the motor vehicle having to be concerned about this. Hereby the safety as well as the comfort for the operator of the motor vehicle can be increased, especially a rolling-away of the motor vehicle and an unnecessary wear of the parking brake can be avoided.